Proper hydration plays a crucial role in health and performance.
Water is the single largest nutrient in the body -- and one of the most important. Water is needed to regulate body temperature, keep skin moist, and transport oxygen and essential nutrients to cells. Yet, our bodies are also constantly losing water, as vapor in breath and as liquid from perspiration and urine, which must be replaced. A loss of just 1 – 2 percent of body water can put a strain on the cardiovascular system, and cause both health and performance to suffer.
Most people can get all the fluids they need from beverages and foods by simply letting thirst be their guide. However, because children, athletes and older adults are more vulnerable to dehydration and certain situations like extremes in climate and altitude can increase fluid losses, it's important to know when paying closer attention to fluid intake is important.
What Experts Say
Laying the Caffeine-Dehydration Myth to Rest - An interview with hydration expert Dr. Ann Grandjean.
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Hydration Calculator
Learn about daily hydration needs and how temperature and intensity affect fluid needs during physical activity. View Tool
Hydration is vital for every aspect of life. It is critical in helping to maintain normal body temperature and for every physiological function.
Learn about the role of hydration in the body with our Hydration & You tool.
Test your hydration knowledge with our Hydration Quiz.
Some people can be more vulnerable to dehydration.
Learn about special hydration considerations for:
How much one needs to drink each day is influenced by a variety of factors. Learn general hydration guidelines, how to monitor hydration status and recognize dehydration.
Learn about ACSM fluid replacement recommendations for athletes.
In Hydration 101, hydration expert Ann Grandjean, EdD, FACSM, CNS discusses common misperceptions about hydration and how advances in hydration science can benefit people at every age and stage of life.
Test your hydration knowledge with our Hydration Quiz.
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- News, Articles and Research Briefs
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Leading Experts Sign Scientific Consensus Statement on the Importance of Hydration in Health
Hydration Guidelines: Highlights from the IOM/NAS Report on Hydration/IOM Hydration Guidelines
Learning to Recognize Dehydration and Monitor Hydration Status
Climate & Altitude Can Affect Fluid Intake and Hydration Needs
Special Hydration Considerations: Fluid Needs and Hydration Tips for Children
Special Hydration Considerations for Aging Adults
Special Hydration Considerations for Athletes - Preventing Dehydration and Overhydration
American College of Sports Medicine (ACSM) Fluid Replacement Recommendations
How to Calculate Your Sweat Rate
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- What Experts Say
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Understanding Exercise-Associated Hyponatremia
In this interview, Dr. Bob Murray, one of the world's leading experts in sports nutrition and hydration, explains exercise-associated hyponatremia and how to prevent it.Hydration 101: More Than Just Water
Ann Grandjean, EdD, FACSM, CNS answers common questions about hydration and advances in hydration science that can benefit people at every age and stage of life.Laying the Caffeine Dehydration Myth to Rest
Hydration expert Dr. Ann Grandjean reviews the research that conclusively confirmed that beverages with caffeine are not dehydrating, as was once commonly believed.Experts Sign Scientific Consensus Statement on Hydration
Hydration experts from around the world reach agreement that research links adequate hydration to survival, health promotion and sustained physical and metal performance.Hydration (Subscription required)
An Evidence Based Review by the American Dietetic Association Evidence Analysis Library. A systematic review of the existing human research on hydration, including the effect of caffeinated beverages on hydration.Exercise and Fluid Replacement
Position of the American College of Sports Medicine (2007). ACSM regularly updates their position on exercise and fluid replacement and hydration recommendations based on the latest research.U.S. Physical Activity Guidelines (2008)
Developed with health professionals and policymakers in mind, this booklet provides science-based guidance to help Americans aged 6 and older improve their health through appropriate physical activity.Sport and Health. EU 2008 Physical Activity Guidelines
Recommended Policy Actions in Support of Health-Enhancing Physical Activity. Fourth Consolidated Draft, Approved by the EU Working Group "Sport & Health" at its meeting on 25 September 2008Physical Activity and Public Health: Updated Recommendation for Adults from the American College of Sports Medicine and the American Heart Association
Powell KE, Blair SN, Franklin BA, Macera CA, Heath GW, Thompson PD, and Bauman A. Circulation 2007;116;1081-1093.Physical Activity and Public Health in Older Adults. Recommendation From the American College of Sports Medicine and the American Heart Association
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Circulation. 2007;116:1094-1105.
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- Webinars, Podcasts and Continuing Professional Education (CPE)
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Hydration & Physical Activity – Risks, Challenges and Benefits (Webinar)
Hydration and Health Promotion (CPE Program)
Kolasa KM, Lacke CJ and Grandjean AC. Nutrition Today 2009 44(5) 190-201.Note: This program is available on Nutrition Today. It is accessible to non-subscribers for a fee.Hydration and Children (Podcast)
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Learn from Dr. Maxine Buyckx why proper hydration is especially important for children.
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- Printable Downloads (brochures, educational handouts and monographs)
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Fluid Needs and Hydration Tips for Children
Based on “Active Healthy Lifestyles. A Guide for Parents” developed by Dr. Marcela Gonzales-Gross and colleagues, this fact sheet can help parents understand the importance of helping children adopt sensible, balanced fitness and nutrition habits. This fact sheet includes fluid needs by age group, signs of dehydration, hydration and physical activity and tips for keeping active kids hydrated.Hydration Matters
Consumer fact sheet covering current U.S. hydration guidelines and the various roles role water plays in the body.Hydration: Does it Always Have to be Water? (IFIC)
This International Food Information Council consumer fact sheet addresses the common misperception that caffeine causes dehydration and provides an overall guide to how all liquids, including milk, fruit juices, sports drinks, watery foods, and even beverages such as soft drinks, coffee and tea can play a role in meeting individual hydration needs.Hydration: Fluids for Life (ILSI-NA)
Scientific monograph on hydration and health written by Ann Grandjean EdD, FACN, CNS and Sheila M. Campbell, PhD, RD for the North America branch of the International Life Sciences Institute (ILSI-NA). Posted with permission.Nutrition for Athletes: A Practical Guide to Eating for Health and Performance (IOC)
The Coca-Cola Company partnered with the International Olympic Committee (IOC) Medical Commission to update and print this publication to help to spread this information, developed by the Nutrition Working Group of the IOC in close collaboration with the IOC Athletes' Commission, to athletes at all levels. Posted with permission.Nutrition for Football: A Practical Guide to Eating for Health and Performance (FIFA)
Prepared for the FIFA Sports Medical Committee by Professor Ron Maughan (UK) Professor Louise Burke (Australia) and Dr. Donald T. Kirkendall, (USA). Based on an International Consensus Conference held at FIFA House in Zurich September 2005. Posted with permission.Nutrition for Athletics: A Practical Guide to Eating and Drinking for Health and Performance in Track and Field (IAAF)
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Written by Professors Louise Burke (Australia) and Ron Maughn (UK). This booklet is based on the conclusions of the International Association of Athletics Federations (IAAF) Consensus Conference on Nutrition for Athletes held in Monaco in April 2007. Posted with permission.
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- Tools for Active Healthy Living (calculators and widgets)
- Related References
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Urinary indices during dehydration, exercise, and rehydration.
Armstrong LE, Soto JA, Hacker Jr FT, Casa DJ, Kavouras SA & Maresh CM. Int. J. Sport Nutr. 1998; 8:345–355.ILSI North America Conference on Hydration and Health Promotion. J Am Coll Nutr 2007; 26: 529S-623S.
Note: The following papers from this conference are available to download free from the Journal of the American College of Nutrition website.Hydration and Health Promotion: A Brief Introduction. Buyckx, ME
Hydration and Disease Manz F.
Hydration and Physical Performance. Murray B. J Am Coll Nutr. 2007;26:542S-548S.
Dehydration and Cognitive Performance. Grandjean AC and Grandjean NR. J Am Coll Nutr. 2007;26:549S-554S.
Assessing Hydration Status: The Elusive Gold Standard. Armstrong LE. J Am Coll Nutr. 2007;26:575S-584S.
Exercise, Heat, Hydration and the Brain. Maughan RJ, Shirreffs SM, and Watson P. J Am Coll Nutr. 2007;26:604S-612S.
Hydration in Children. Manz F. J Am Coll Nutr. 2007;26:562S-569S.
How Primary Care Providers Might Review Evidence on Hydration. Kolasa KM, Lackey CJ, and Weismiller DG. J Am Coll Nutr. 2007;26:570S-574S.
Limitations of Data on Fluid Intake. Fulgoni,VL J Am Coll Nutr. 2007;26:588S-591S.
Hydration Needs throughout the Lifespan. Campbell SM. J Am Coll Nutr. 2007;26:585S-587S.
Role of Whole Foods in Promoting Hydration after Exercise in Humans. Sharp RL. J Am Coll Nutr. 2007;26:592S-596S.
Hydration at the Work Site. Kenefick RW and Sawka MN. J Am Coll Nutr. 2007;26:597S-603S.
The Effect on Hydration of Two Diets, One with and One without Plain Water. Grandjean AC, et. al. J Am Coll Nutr 2003; 22(2):165-173.
Exercise and Fluid Replacement. Position Stand of the American College of Sports Medicine. Med & Sci Sports & Exerc 2007; 39(2) 377-390.
Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. (2004) Institute of Medicine (IOM) Food and Nutrition Board.
American Dietetic Association Evidence Analysis Library - Hydration. The American Dietetic Association has conducted a systematic review of the existing human research on hydration, including the effect of caffeinated beverages on hydration. (Subscription required)
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- Related Websites (additional information)
- Frequently Asked Questions
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How much water do people need to drink each day?
There are no specific recommendations for plain water. However, the Institute of Medicine of the National Academy of Sciences (IOM) does have recommendations for total fluid intake from all sources, including plain water, foods and beverages. According to the IOM, adult men and women should aim for 11.5 to 16 cups (2.7 to 3.7 L) of total fluids a day from food and beverages (including plain drinking water), while children and adolescents need slightly less, about 10 to 14 cups (2.4 to 3.3 L) per day.See IOM hydration guidelines.On a daily basis, most people get enough fluid through normal drinking behavior, such as drinking with meals and snacks. But, children, older adults, people working in hot climates and those who exercise vigorously should pay close attention to their hydration needs.What 'counts' toward hydration?
Drinking water, other beverages, and the water present in foods all play a role in keeping the body hydrated. According to the IOM, Americans obtain 80 percent of their total fluids each day from drinking water and other beverages, and about 20 percent from high water-content foods, like soup, fruits and vegetables. As a result, the IOM suggests that for proper hydration, American adult males need to drink about 13 cups (3 L) of fluids each day, which can come from drinking water as well as other beverages, while adult women need to drink about 9 cups (2.2 L).Plain water is always a great choice for meeting hydration needs, but it's not the only one. The IOM has determined that when it comes to meeting daily hydration needs, all beverages, including those with caffeine, are hydrating. Although older studies showed that caffeine can have a mild, short-term diuretic effect in individuals who do not normally consume caffeine, more recent studies have shown that this is not the case for people who regularly consume caffeine. That's because the body can adjust to the presence of caffeine in about three to five days of regular use, which greatly diminishes its weak diuretic effect.Is it possible to drink too much water?
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Yes. Excessive water drinking can dilute blood sodium levels and cause a dangerous electrolyte imbalance, which can lead to disorientation, confusion, seizures, and even death.In adult athletes, over-hydration (hyponatremia) can occur if a great deal of fluid and electrolytes are lost through sweat but only electrolyte-free fluids are consumed, or if water consumption over several hours far exceeds water losses (including sweat loss). The latter situation can be a concern for women, who tend to have lower sweat rates than men. It is a particular concern for small, slow runners participating in long-distance events who, even though they do not sweat very much, drink very large amounts of water during or right after an event. Unfortunately, signs of hyponatremia are difficult to distinguish from heat exhaustion or heat stroke. Therefore, the best defense during exercise is developing a smart hydration plan, which includes drinking to your sweat rate to help avoid overdrinking.
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